1. Field of the Invention
The present invention relates to a coupling assembly and more specifically to a pneumatic coupling assembly for use in providing an air start for aircraft.
2. Description of the Prior Art
In the past, coupling assemblies have been used to couple ground equipment providing for a high pressure air flow to an aircraft for starting the aircraft engine. In general, these coupling assemblies operate with a push-pull operation wherein, the coupling assembly is pushed to engage an external coupling nipple on the aircraft, and it is pulled to release the coupling assembly. When the coupling assembly is engaged, this allows for the transferance of high pressure air from the ground equipment to the aircraft for use in starting the aircraft engine or in providing other functions while the aircraft is on the ground. The coupling assembly normally would include a valve so as to restrict the flow of any high pressure air when the coupling assembly is removed from the aircraft nipple. The valving therefore acts as a safety feature to prevent the coupling assembly and hose from causing damage or injury if the coupling assembly uncouples during use or if the coupling assembly is removed while the ground equipment is still providing high pressure air.
The prior art coupling assemblies generally included a butterfly valve, pivoted around a shaft located in the center of the passageway through the coupling assembly. The use of the butterfly valves positioned at a central position within the air flow path restricts the air flow even when the valves are in the open position and also allows for standing waves to be created in the air path. The location of the valves in the central position may restrict the flow of air up to twenty-five percent (25%) of the air flow if the passageway were unrestricted. In general, the prior art butterfly valves either consist of a single butterfly valve pivoted from the central position or a pair of butterfly valves each pivoted from the central position.